As anthracycline family of antibiotics, daunomycin (refer to U.S. Pat. No. 3,616,242) and adriamycin (refer to U.S. Pat. No. 3,590,028) have heretofore been known, which can be obtained from a culture broth of actinomycetes, and these compounds have a broad tumoricidal spectra against experimental tumors and are being utilized broadly as chemotherapeutic agents for cancers treatment. However, daunomycin and adriamycin in fact show a fairly strong anticancer effect, while these have some strong side-effects such as a severe cardiotoxic effect, and therefore, these are not sufficiently satisfactory as a therapeutic agent. Accordingly, attempts to obtain the analogous compound with improved therapeutic efficacy have been made by fermentation method, semi-synthetic method, microbial transformation method and the like other various means. For instance, U.S. Pat. No. 3,988,315 illustrates aclacinomycins A and B; Journal of Antibiotics (Vol. 33, pages 1331-1340), Topics in Antibiotics Chemistry (Vol. 12, pages 102-279, published by Ellis Horwood Limited) and U.S. Pat. No. 4,355,026 illustrate 4-demethoxy-11 -deoxydaunomycin; and U.S. Pat. No. 4,316,011 illustrates rhodomycin group antibiotics. ("published unexamined Japanese patent application".)
Various kinds of anthracycline antibiotics have been proposed as anticancer agents, as mentioned above; some of them have already been used for cancer chemotherapy and some others are in clinical trial. However, none of them is satisfactory both in toxicity and anticancer efficacy. Moreover, results of anticancer agents obtained with in vitro and in vivo tests using experimental tumors are not always reflective directly on anticancer effect against human and therefore, investigations are required from various viewpoints. For this reason, it has been desired to propose compounds belonging to a further new class, with respect to anthracycline antibiotics which have been evaluated in a way.